Preparation and characterization of pre-silane modified ethyl cellulose-based microcapsules containing linseed oil

Abstract

In this study, ethyl cellulose (EC) was treated with three different trimethoxysilane coupling agents. Various characterization techniques were employed to evaluate silane modification of EC compound. Microencapsulated phase change materials based on linseed oil (LO) core and un-treated and silane-treated EC shell materials with ratio of LO to EC (70:30) were prepared by solvent evaporation method. Morphology and shape of microcapsules were studied using optical microscopy and scanning electron microscopy (SEM) equipped with energy dispersive X-ray analyzer (EDAX). The size distribution of microcapsules was evaluated using a particle size analyzer.Fourier transform infrared spectra (FTIR) and nuclear magnetic resonance (NMR) analyses revealed chemical interactions between EC and three different types of trimethoxysilane. Chemical bond (SiOC) was formed by the reaction between SiOH and the hydroxyl group of EC. The thermo-gravimetric analysis (TGA) showed 6–12wt% silane grafting on the EC compound. Microcapsules with a uniform spherical shape 5–35μm in diameter and 0.5–2.0μm in shell thickness were successfully prepared using either un-treated or silane-treated EC. SEM micrographs of the fractured surface of acrylic coating containing LO filled EC-microcapsules showed matrix structure for microcapsules, as results of silane treatment of EC shell material.The pre-silanized EC-microcapsules can improve mechanical properties of water-based self-healing coatings, due to better compatibility of microcapsules with polymeric matrix and possible chemical interactions between silane groups attached on EC-microcapsules and functional group of polymeric matrix.